Reported here are several deviations (n = 15; 1·96%) from typical morphology in a large sample (n = 767) of European brook lamprey Lampetra planeri from a single population in the Loch Lomond catchment; this includes one specimen bearing a true anal fin. A brief review of petromyzontid teratology is provided.
Keywords: Loch Lomond; abnormality; jawless; non-parasitic..
© 2014 The Fisheries Society of the British Isles.